OCULAR FUNGAL INFECTIONS Ayse Kalkanci MD1, Sengul Ozdek MD2, Mehmet Cuneyt Ozmen MD, FICO3 1 Professor in Medical Microbiology Department, Gazi University Faculty of Medicine, Ankara, TURKEY 2Professor in Ophthalmology Department, Gazi University Faculty of Medicine, Besevler Ankara, 06500, TURKEY 3 Assistant Professor in Ophthalmology Department, Gazi University Faculty of Medicine, Besevler Ankara, 06500, TURKEY 2 DEDICATION FROM AYSE KALKANCI I dedicate this book to my family; my beautiful Defne and my sweetheart Bora, my loving parents Leman and Cengiz Seçkin, my dearest sisters Hande and Dilek, their wonderfull husbands Barış and Rasim, and my smart nephew Zeynep. DEDICATION FROM SENGUL OZDEK To my invaluable family. DEDICATION FROM MEHMET CUNEYT OZMEN In memory of my father… For the three beautiful women of my life; my mother, my wife, and my daughter. 3 4 FOREWORD Infectious diseases of the eye have been recognized as an important cause of blindness. As a relatively uncommon cause, fungi have been isolated from a variety of ocular infections including keratitis, scleritis, canaliculitis, endophthalmitis and orbital cellulitis. Fungi are recognized as opportunistic pathogens. Ocular fungal infections (ophthalmic mycoses) are important causes of morbidity, blindness and even mortality especially in tropical countries. This book will focus on laboratory diagnosis and experimental models of ophthalmic mycoses as well as clinical features of fungal keratitis, endogenous and exogenous endophthalmitis. An outline of ocular anatomy will be given before detailing fungal infections. Ayse Kalkanci, MD Sengul Ozdek, MD M. Cuneyt Ozmen, MD 5 6 TABLE OF CONTENTS PAGE 1. OCULAR ANATOMY 9 2. ETIOLOGICAL AGENTS AND EPIDEMIOLOGY 11 3. CLINICAL DIAGNOSIS AND TREATMENT 17 3.1. FUNGAL ENDOPHTHALMITIS 17 3.1.1. Endogenous fungal endophthalmitis 17 3.1.2. Exogenous fungal endopthalmitis 23 3.2. FUNGAL KERATITIS 25 3.3. ORBITAL INFECTIONS 35 4. COLLECTION AND TRANSPORTATION OF 41 SPECIMENS 5. LABORATORY DIAGNOSIS 45 5.1. CONVENTIONAL MICROBIOLOGIC 47 TECHNIQUES 5.2. HISTOPATHOLOGIC TECHNIQUES 57 5.3. IMMUNOLOGIC TECHNIQUES 58 5.4. BIOCHEMICAL TECHNIQUES 59 5.5. MOLECULAR TECHNIQUES 59 5.6. OTHERS 65 6. EXPERIMENTAL MODELS 65 6.1. IN VIVO MODELS 65 6.1.1. Mouse models 66 6.1.2. Rabbit models 67 6.1.3. Rat models 68 6.1.4. Other models 68 6.2. IN VITRO MODELS 69 7. REFERENCES 71 7 8 1. OCULAR ANATOMY (Figure 1) Eye can be divided into 3 segments for the purpose of education as: 1. Eyelids and lacrimal system, 2. Orbits and adjacent soft tissues, 3. Eyeball: anterior and posterior segments Crystalline lens EOM Anterior Chamber CRV Cornea Optic nerve Vitreous Iris Retina Sclera Choroid Ciliary Body FIGURE 1. Anatomy of the eyeball. (EOM: Extraocular muscle, CRV: Central retinal vessels) Eyelids are protective barriers for the globe. They protect the globe from dangers of the outside world. There is an orbital septum in each eyelid which acts as a barrier for the prevention of spread of infections through the orbital soft tissues. Conjunctiva, the innermost lamella of the eyelid and outermost structure of the globe, is another barrier for microorganisms on the anterior surface of the globe from freely entering into globe or orbital soft tissue along its surface. Lacrimal system is composed of a secretory part; lacrimal gland, accessory lacrimal glands in conjunctiva, and an excretory part; starting from puncta, canaliculi, lacrimal sac, nasolacrimal canal ending in the inferior meatus of the nose. Tears protect the globe from infections by rinsing the surface of the eye.1 Orbits are cone shaped bony cavities which involve the globes, extraocular muscles, fat and other soft tissues. They consist of seven bones forming a safe room for the 9 globes. The periosteum of the orbita fuses anteriorly with the orbital septum and posteriorly with the dura mater. Abscesses usually localize in the subperiosteal space. The roof, medial wall, and floor of the orbit are neighbours of paranasal sinuses, (the maxillary, frontal, ethmoid, and sphenoid sinuses). The paranasal sinuses may be the source of an orbital infection because of this close anatomical relationship. Medial orbital wall is the thinnest of the orbital walls and is the weakest point for the orbits. Infections of the ethmoid sinus in children commonly extend through the intact lamina papyracea (medial wall) causing preseptal and orbital cellulitis. The lateral wall of the sphenoid is also the medial wall of the optic canal. Therefore, infections of the sphenoid sinus may involve the optic nerve, resulting in visual loss or visual field abnormalities. Direct communication between the orbit and adjacent structures, through the apertures like the superior and inferior orbital fissures, nasolacrimal duct, and the optic canal may serve as a direct passage for an infectious process between the orbit and surrounding structures.1 Eyeball is composed of 3 layers: outermost is the fibrous layer consisting of cornea and sclera, middle layer is uvea consisting of iris (anterior part), ciliary body (middle) and choroid (posterior), and the innermost layer is retina. Crystalline lens and iris divides the eyeball into chambers like anterior and posterior chambers which are full of aqueous humor secreted by nonpigmented epithelium of the ciliary body, and vitreous space which is full of gel like vitreous. 1 Defense mechanisms of the eye start from eyelids, eyelashes, tear film, cornea and conjunctiva with blink reflex and by providing mechanical barrier. In addition to mechanical washing of the ocular surface, tear film contains several immunologically active substances necessary for ocular defense. The mucin contained in tears prevents adhesion of Candida species to contact lenses, likely by entrapping the microorganisms.2 Fungal infections of the eye will be discussed according to the anatomical part of the eye involved in the disease. 10 2. ETIOLOGICAL AGENTS AND EPIDEMIOLOGY The incidence of ocular fungal infections has increased substantially over the past decades because of the increased number of patients with acquired immunosuppression secondary to extended use of immunosuppressive agents, long term broad spectrum antibiotics and AIDS.3-7 The pathogenesis of eye infections is linked to the epidemiology of disease. The term of endogenous endophthalmitis indicates to blood borne spread of microorganisms into the eye. Mainly, neutropenic immunosuppressive patients undergo blood borne infections and fungemia. Candida species are the most common cause of endogenous endophthalmitis which usually develop in immunocompromised patients having chronic underlying systemic disease, an associated septicemia for which broad spectrum systemic antibiotic therapy is being administered, intravenous hyperalimentation with chronic indwelling catheters or an organ transplantation that requires immunosuppression.8-10 Intravenous drug abusers, patients with diabetes and AIDS are also at high risk for endogenous fungal endophthalmitis (FE). Abdominal surgery is another risk factor for candidemia and hence for endophthalmitis. Common end organ target of fungemia is eye in many cases. But the reason of this tropism is unknown.11-13 Aspergillus species are the second most common cause of endogenous fungal endophthalmitis. Aspergillus flavus, A. fumigatus, A. niger, A. terreus, A. glaucus, A. nidulans have been reported to cause endophthalmitis. Neutropenic patients or patients receiving corticosteroids, intravenous drug addicts, solid organ transplant recipients are at particular risk for endogenous endophthalmitis with Aspergillus species.12,14 There are several reported cases representing other emerging pathogens such as Fusarium, Penicillium, Pseudallescheria, Cryptococcus species, dimorphic fungi Histoplasma capsulatum, Blastomyces dermatitidis, Sporothrix schenckii, Coccidioides immitis caused endogenous endophthalmitis.12 Exogenous fungal endophthalmitis occurs by inoculation of pathogens into the eye from, trauma or intraocular surgery and usually follows keratitis. Patients with exogenous endophthalmitis are rarely immunocompromised. Therefore any of the 11 saprophytic fungi found in natural habitats, may cause exogenous infection of the eye. The mycotic causes of exogenous endophthalmitis are mainly Candida species especially in postsurgical group5,14, whereas Fusarium species were found only in the posttraumatic and postkeratitis groups.15,16 An epidemic of postsurgical endophthalmitis with Candida parapsilosis has been reported representing 15 patients had ocular surgery over a 3-month period of time.17 At the time of surgery all eyes were learnt to be irrigated with a solution from the same lot that was contaminated with C. parapsilosis. Paecilomyces, Aspergillus, Acremonium, Exophiala, Pseudallescheria, Syctalidium, Sporothrix, Penicillium species were also reported as the etiological agents of exogenous endophthalmitis cases.18 Fusarium species were the most prevalent (30%) organisms, followed by Aspergillus species (13.3%), Acremonium species (8.3%) and Paecilomyces species (8.3%). Other moulds were the causative agents only in 13.3% of the cases.18,19 Candida species were more prevalent especially in postsurgical group, whereas Fusarium species were found only in the posttraumatic and postkeratitis groups.16,20 Fungal pathogens in posttraumatic endophthalmitis are numerous and similar to those causing fungal keratitis. Reports include Exophiala jeanselmei, P. boydii, A. niger, Scytalidium dimidiatum, Helminthosporium